Common rail injectors are injection systems for internal combustion engines, which operate according to the storage injection principle, using a common high-pressure fuel storage for all cylinders of an internal combustion engine. Piezoelectric actuators and piezoelectric controllers, for example, CRI3.1, CRI3.2, CRI3.3 from Robert Bosch GmbH having various functions, are used for operating an injector. One object of these functions is to minimize the tolerances throughout one exemplar and one service life of the injection system.
The IVA (injector voltage adjustment) is provided ex factory as a first function for equalizing the voltage of various injectors. For this function, the voltage demand of each injector is measured at the time of its manufacture and is stored in the EEPROM of a control unit at the time of installation for controlling the injection system via a code, defining the so-called IVA class.
With regard to the second function, the NVC (nominal voltage calibration) is taken into account for equalizing the drift in the voltage demand over the service life.
A method for ascertaining the triggering voltage of a piezoelectric element is known from DE 103 15 815 A1. In this method, a voltage drop is detected on the piezoelectric element after a charging operation. The triggering voltage of the piezoelectric element is determined from this voltage drop.